Panthera Tigris said:I don't consider a homosexual relationship to be immoral. It's not my personal cup of tea, but as long as it is between two consenting adults, who are we to judge?
In accepting that, how can we not accept the same arguments for relationships between close blood relations. Sure, it might not be our own personal cup of tea (there are so many beautiful girls out there, why the hell would I want to get with my sister!!.....no offense intended sis...), but how can we justify judging it as immoral if it is two consenting adults? Surely like consenting homosexual couples, what they do is nobody else's business?
Like I say, the original article that took my interest was a pair of half siblings who hadn't been raised together in a single family unit. So not your conventional sibling scenario. But with society and the family unit changing, that kind of example could well become more common.
I don't have any real problem with the people in your scenario being married.
That's a personal opinion. I do, however think that it's an unusual and specific situation, and, like any moral hypothetical, prompts interesting questions.
Most situations involving incestuous relationships would have abhorrent power imbalances, grooming, and issues with age of consent. It is not an equivocation of same sex relationships.
More importantly, it is not relevant to the discussion. It is a specific, unusual case that would require its own discussion. It has nothing to do with the question 'Should the law be changed to allow same sex marriage?'